So with various novel coronavirus vaccines now in circulation there is a lot of information that most people honestly do not have the tools to digest. Two of these include the varying efficacies of the vaccines and secondly why we still need to wear masks for a while. The answers to both of those questions have their roots in understanding that a pandemic is overcome by large volumes of the population having sufficient long lasting immunity to prevent the virus from spreading and replicating. I will address the first issue today.
Firstly, vaccines have worked for a long time to suppress and eradicate infectious diseases. This time is no different, it will work. The prerequisite of course is that enough of the population gets vaccinated. Suppression and eradication is a population effort and effect. Viruses cannot live on their own, they need a host, in this case, humans. The more hosts it gets into and the more it defeats a host’s immune system, the more the virus replicates and the more it mutates. Replication means more virus is able to be transmitted/spread and mutation increases the likelihood of a more dangerous virus because viruses mutate in an effort to survive the battle against the immune system, thereby increasing the probability of new more dangerous strains. I make these points to underscore the importance of treating the entire (large percentage of) population to stop the pandemic.
If you understand this then you can understand that regardless of whether a vaccine has 95, 85 or 65% efficacy, if many people take it, all will significantly reduce the amount of virus in the population thereby helping eradicate the infectious agent. Additionally one must be careful to judge a vaccine versus another purely on surface efficacy numbers. For example the newest Johnson and Johnson vaccine was tested in a population in which the new more dangerous variant first identified in South Africa was rampant and still maintained overall 66% efficacy for moderate and severe disease and 100% efficacy against any hospitalisations or deaths. Pfizer and Moderna’s vaccine, although excellent (read more here) at 95% efficacy and still seemingly very effective as the new variants spread within the USA, was not tested in a population that had high levels of the South African variant during the clinical trials so we do not know what the initial efficiacy numbers would have been if they had been tested within a population rampant with the new variants.
Additionally, well established vaccines used in routine immunisations all vary in efficacy and have still worked to suppress and eradicate the diseases they were built to treat, see a comparison chart at the end of this article (keep in mind though that each virus is markedly different so comparison is being used loosely). Some vaccines require many doses some 1, some offer limited immunity requiring boosters, some offer lifelong immunity, some offer almost perfect immunity within the population that receives the vaccine, some have much lower numbers and yet all are routinely given because the benefit to the population is profound.
Another consideration that will become apparent in time is that one of the COVID-19 vaccines may work better in the elderly or in those with diabetes or some such advantage that will lead to more focused guidelines for who should get which.
The main point is: don’t be too quick to judge numbers without context and take any vaccine that you can get to contribute to herd immunity!
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Adapted from the CDC and WHO
|Vaccine||Efficacy (moderate and severe disease)||Doses|
|COVID-19 Astra Zeneca||63%||2|
|COVID-19 Johnson and Johnson||66%||1|
|Influenza||40-60% (changes each year)||1 dose per year|
|Rubella||97%||1 or 2|
|Varicella (Chicken Pox)||90%||2|
|Haemophilus Influenza B||95||2 or 3|